The combination of his love for collecting, for history and for his family resulted over time in the Paul Markham Kahn Collection of Hawaiiana, one of the world's most important collections of its kind. Assembled over a period of forty years, the Collection preserves a comprehensive body of Hawaiian material, including printed books, manuscripts and periodicals, with particular emphasis on ancient culture, Western contact with the Pacific islands, and the resulting processes of change: cultural, political and ecological.

The scope and importance of the material was recognized when the State of Hawaii acquired the collection for the Hawaii State Archives.

Paul Kahn in his library commenting on his collection